[Peter B. kenington, “High Linearity RF Amplifier Design”, Artech house Microwave Library, ISBN 1-58053-143-1.] and the like propose a Doherty amplifier as an efficient power amplifier. The Doherty amplifier includes a carrier amplifier and a peak amplifier. The carrier amplifier operates constantly while the Doherty amplifier is in operation. The peak amplifier operates when the Doherty amplifier outputs high power. The carrier amplifier and the peak amplifier may have different temperatures owing to the different operating time and operating efficiencies thereof.
A power amplifier has I/O characteristics that vary depending on temperature. That is, the nonlinearity of the power amplifier varies depending on temperature, and thus the temperature is adjusted (by warm-up and the like) to allow the power amplifier to be used within a desired temperature range. For example, a transmission amplifier described in JP-A 2004-328710 (KOKAI) (for example, page 16 and FIG. 1) includes means for detecting temperature and means for promoting self-heating of an amplification section. Based on the results of temperature detection, the transmission amplifier controls the means for promoting to carry out warm-up.